Buildings and Cities

Net Zero Buildings

The Rocky Mountain Institute Innovation Center is a net zero building on the north shore of the Roaring Fork River in Basalt, Colorado. The two-story, 15,600-square-foot building was constructed using Integrated Project Delivery software and model, a replicable process that can be employed by commercial projects around the country of similar scale. Although located in one of the coldest climate zones in the United States, the insulated building envelope was built with R-50 walls and R-67 roof. It has an 83-kilowatt solar photovoltaic system on the roof that provides more energy than the building is designed to use. The building was designed to use less water than the rain and snow that fall upon the site. Although graywater use is not allowed as yet in Colorado, a graywater system was installed in anticipation of changes in state regulations. To save heating and air-conditioning energy, the Center focused on heating and cooling people, not the space. They addressed the six factors that affect human comfort, which are air temperature, wind speed, humidity, clothing level, activity level, and the temperature of surrounding surfaces. By zeroing in on these factors, the Center has a broader range of comfortable air temperature, from 67 to 82 degrees Fahrenheit compared to the conventional commercial building range of 70 to 76 degrees. This cut energy use by 50 percent, eliminated the air-conditioning system, and requires a small heating system only on the coldest days.

A net zero building is one that has zero net energy consumption, producing as much energy as it uses in a year. In some months it may generate excess electricity through distributed renewables; at other times it may require electricity from the grid. On balance, it is self-supporting. Net zero buildings are more resilient during disasters and blackouts, are more carefully designed by necessity, and generally have reduced operating costs.

Designing a net zero building means seeing a building as a system and addressing the sources of energy use. There are multiple ways to reduce a building’s energy loads, including:

Daylighting,

Maximum insulation,

Electrochromic glass,

Passive solar design, and

Advanced heating and cooling.

Net zero buildings were once a novelty, but are becoming more commonplace, as architects roll out extraordinary buildings across the world. There is now a Walgreens drugstore in Chicago that is a net zero building. Net zero neighborhoods, districts, and communities are also being designed and constructed. Newer net zero buildings push the margins further: zero water and zero waste. They harvest rainwater and process sewage on-site into compostable forms.

Impact: There are no numbers on this page because net zero buildings are a mosaic of separate solutions. They draw on smart windows; green roofs; efficient heating, cooling, and water systems; better insulation; distributed energy and storage; and advanced automation. All are treated individually in our analysis. If net zero buildings are calculated as a single solution, assuming 9.7 percent of new buildings will be net zero by 2050, the integrated opportunity is 7.1 gigatons of carbon dioxide.

“Net zero” refers to new buildings which are either “net zero energy” or “net zero carbon.” Net zero energy buildings are energy-efficient and consume zero energy from utility-scale sources on an annual basis because all the power the building needs is generated through on-site renewable energy. Net zero carbon buildings produce net zero carbon emissions on an annual basis. The definition of zero carbon varies across countries and may include an element of carbon offsetting. For the purposes of this analysis, net zero buildings are considered as new net zero energy buildings.

Methodology

Net zero buildings encompasses several solutions in the Buildings and Cities and Energy Sectors that have been modeled individually by Project Drawdown. Net zero buildings can involve all Drawdown solutions modeled, including the installation of better insulation, energy-efficient glazing, more efficient lighting, improved HVAC, efficient water heating, optimized building system controls, distributed renewable energy systems, etc.[1] Since these solutions were modeled separately, net zero buildings were not modeled independently in order to avoid double-counting.

Results

The emissions and financial impacts of net zero buildings are included in individual solutions in order to avoid double-counting. For more information, see the Sector Summary: Buildings and Cities link below.

In order to assess the overall potential of net zero buildings, however, estimates were made based on several future adoption cases derived from the American Institute of Architecture 2030 Challenge framework targets, LEED Platinum building adoptions as a proxy for net zero buildings, and New Building Institute (NBI) current adoption data and growth rates for net zero buildings projects. The potential emissions reduction impacts ranged from 5 to 32 gigatons of carbon dioxide-equivalent, depending on the adoption rate society chooses to implement. If net zero buildings adoption is projected based on using the NBI data, an estimated 9.7 percent of new buildings could be net zero by 2050, with a cumulative emissions reduction of 7.1 gigatons of carbon dioxide-equivalent.

Discussion

The building industry has the potential to have a large impact on drawing down greenhouse gas emissions. There are many different energy efficiency strategies to reduce the impact of buildings. In addition to this, on-site energy generation takes buildings a step further to reduce their impacts. The ideal solution combines both of these strategies with buildings generating as much renewable energy as they consume on an annual basis. This is the essential concept of net zero buildings. In this way, net zero buildings combine many other Drawdown solutions into one elegant concept for humans to strive towards.

In practice, net zero buildings help drive design teams and owners to design and make investments in energy conservation measures and on-site energy generation. The projections of performance are based on a number of factors that could change significantly based on the decisions made by society. For example, if energy efficiency and production along with polluting greenhouse gases were properly priced, the adoption rate of net zero buildings would be much higher. It is plausible that most new buildings could achieve net zero status now if society priced the driving factors around them properly.

[1]Net zero buildings comprise some undefined combination of solutions relevant to the particular characteristics of the building in question in order to achieve net zero status.